We now proceed to discuss the properties of marrow; for this is
one of the liquids found in certain sanguineous animals. All the
natural liquids of the body are contained in vessels: as blood in
veins, marrow in bones other moistures in membranous structures of the
skin

In young animals the marrow is exceedingly sanguineous, but, as
animals grow old, it becomes fatty in animals supplied with fat, and
suet-like in animals with suet. All bones, however, are not supplied
with marrow, but only the hollow ones, and not all of these. For of
the bones in the lion some contain no marrow at all, and some are only
scantily supplied therewith; and that accounts, as was previously
observed, for the statement made by certain writers that the lion is
marrowless. In the bones of pigs it is found in small quantities;
and in the bones of certain animals of this species it is not found at
all.